Electric circuit control means



A. BOYAJIAN ELECTRIC CIRCUIT CONTROL MEANS May l2, 1936.

Filed Dec. 25, 1932 2 Sheets-Sheet 1 ACCURPENT k' 4' Pg). 3C. Ffgd- IDc=O I 8C 5 CURRENT IAC: '00% CURRENT IAc= |00% His Attorney.

May 129 19360 A BOYAJIAN 2,040,684

ELECTRIC CIRCUIT CONTROL MEANS Filed DeC. 23, 1952 2 Sheets-Sheet 2 Invent or: zram Boyajiam Iliff, ,j v M-em HIS Attorney Patented Mayl2, 1936 UNITED STATES 'PATENT OFFICE ELECTRIC CIRCUIT CONTROL MEANS Aram Boyajlan, Pittsfield, Mass., assigner to General Electric C New York Application December 23, 1932, Serial No.

ompany, a corporation of 22-Chims. (Cl. 171-119) including circuit elements having non-linear voltampere characteristics.

Various investigators have made theoretical studies of the resultant volt-ampere characteristics of combinations of circuit elements in which is combined with an inductance tinguished by non-linear volt-ampere characteristlcs. Throughout the specification and claims, non-linear element or circuit will be used 4to designate an element, circuit, or branch circuit having a non-linear volt-ampere characteristic for effective values of alternating current.

The non-linear element of the type ot'circuit referred to above has usually been an iron-core inductance of the self-saturating type, for example, a reactor in which the core is caused primarily by the alternating with sinusoidal voltage Orharmonics in the voltage wave with sinusoidal current. Such distortion is intensied with increasing alternating current saturation in inductances with ferromagnetic However, I have discovered that if a desired large reactive current is caused to ow as a consequence of direct-current excitation of the increased alternating voltage. In general' for the range of commercial alternating iiux densities the Wave-shape of the current improves with increase in the direct-current excitation over a wide range. As a consequence of the improvement in wave-form the percentage utilization of the capacitance, in circuits of the type previously mentioned, is more complete, and

' stamt-bias saturable to provide an tially a minimum.

It is another object of my invention to a new and improved combination of a capaci- In accordance vention a circuit having a linear with one embodiment of my inelement, such as a capacitance, 30 volt-ampere characteristic is conobtain 'a total acteristic similar to 1 inductance and the capaci? tance.

My invention win be better understood from hg y,

following description taken in connectionk with 55 provide 20 the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings. Fig. 1 is a diagrammatic representation of a combination of a capacitance element having a linear volt-ampere characteristlc and a fixed-bias saturable inductance element, arranged in series relation; Fig. 2 is a diagrammatic representation of the same elements in parallel relation; Fig. 3 is an explanatory diagram showing the volt-ampere characteristic of the diiierent circuit elements severally; Figs. 3a and 3b are explanatory diagrams showing comparative volt-ampere characteristics of self-saturatlng and biased reactors; Figs. 3c and 3d are explanatory diagrams showing comparative culrent waves `ietween a self-saturatlng reactor and a biased reactor; Figs. 4 and 5 are explanatory diagrams showing the volt-ampere characteristics of the series and parallel combinations respectively for different values of the capacitance element; Figs. 6 and 7 are diagrammatic illustrations of an embodiment of my invention in a simple series and parallel circuit, respectively, with a self-saturatlng reactor; Figs. 8 and 9 are diagrammatic illustrations of an embodiment of my invention as applied in current transformer circuits; Fig. l0 is a diagrammatic illustration of an embodiment of my invention in a voltage regulating system; Fig. 11 is a diagram for explaining the operation of the arrangement illustrated in Fig. 10; Fig. 12 is an explanatory elementary diagram of a circuit in which the ratio between the direct current and alternating current of a saturable reactor is maintained constant; Figs. 13 and 14 are explanatory diagrams of volt-ampere characteristics of the circuit shown in Fig. 12 for different ratios between the direct and alternating current of the reactor; Fig. 15 is an elementary diagram of an embodiment of my invention with variable direct current bias in a regulating system; Fig. 16 is an explanatory diagram for the circuit shown in Fig. 15; and Fig. 17 is a modification of the arrangement illustrated in Fig. 15.

While, in general, especially in the ranges proposed for practical use, the harmonics are relatively small, and the shape of the characteristic curve is substantially the same for the fundamental frequency component of the total current or voltage as for the total current or voltage itself, yet, in certain other ranges, the characteristic curve for the fundamental frequency component may be considerably different from that of the total current or voltage. In the specification and drawings, therefore, it is intended that the characteristic curves given represent primarily the fundamental frequency component of the current or voltage when this is different from that of the total current or voltage.

It is further recognized that inductive reactors may have appreciable power losses, represented by in-phase components in their currents or voltages. These components are also usually small and do not modify appreciably the shape of the characteristic curves. However, the characteristic curves, discussed hereinafter, represent strictly the wattless components of the current and voltage.

Referring to Fig. 1 of the drawings, Ill indicates a source of alternating current connected to energize in series relation a capacitance 'II and a saturable inductance I2 having a nxed directcurrent bias and comprising alternating-current windings I2' and a saturatlng winding I3 connected to be energized from a source of direct current Il. The inductance element I2 may comprise various constructions known in the art, auch for example as has been employed in certain types of reactors in which a four-legged core is provided.

This is the diagrammatic form illustrated in Fig. 1 and it is to be understood that this form is i1- lustrative of a suitable form for the similar biased saturable reactors schematically indicated in the remaining figures. In the diagrammatic form illustrated in Fig. 1 the respective alternating current windings I2 are wound in opposite dlrections and are placed on the two inner legs of a fom-legged core structure I2". The single satuiating Winding I3 is wound so as to surround both inner legs as shown in Fig. 1 and similarly indicated in the remaining figures of the drawings. Various other known arrangements may be used. such as the well known three-legged type, where the alternating current windings are wound on the outer legs and connected in parallel relation and the saturating winding is placed on the middle leg. Whatever form of biased reactor is employed in carrying out my invention, it is preferable to use some form in which the direct current circuit is protected from induced alternating .voltages or currents of both the fundamental component of current or voltage and harmonic components of current or voltage.

In Fig. 2 of the drawings the same impedance elements are connected to be energized in parallel relation from the source I0.

If the bias or direct-current excitation of the inductance I2 is unchanged during the application of gradually increasing alternating voltage to the windings I2', a non-linear volt-ampere characteristic similar to curve R in Fig. 3 is obtained. Similarly, if the alternating voltage is applied to the capacitance unit II, linear voltampere characteristics will be obtained such as are illustrated by curves C1 and Cz; the characteristics being of different slopes depending upon the magnitude of the particular capacitance in the circuit.

Fig. 3a shows volt-ampere characteristics of a saturable reactor of the four-legged type schematically illustrated in the drawings with simultaneous direct current and alternating current excitation. The volt-ampere curve for combined D. C.A. C. excitation has two bends-one at the lower densities and the other at the higher densities. The volt-ampere curve for pure A. C. has l also two such bends but since the lower bend occurs at extremely low core densities and small values of current, it does not show in the usual curves drawn for the working range of current and voltage. If the initial portion of the A. C. volt-ampere curve for zero D. C. is drawn to a larger scale, it looks as shown in Fig. 3b, exposing the lower bend. By reference to Fig. 3a, it will be evident that the addition of D. C. excitation indicated by the nume als on each curve does not introduce a new bend vto the curve but shifts the two bends of the A. C. volt-ampere curve far to wards the higher values of current and voltage and this fact makes it possible to correlate the volt-ampere characteristic of the biased reactor with the volt-ampere characteristic of a given capacitor to obtain the various total characteristics utilized in carrying out my invention.

Figs. 3c and 3d indicate very generally the improvement in wave form which may be obtained with a biased reactor as compared with a simple self-saturatlng reactor. Normally the wave shape of the exciting current of a simple closed core reactor departs considerably from a sine wave, when sine wave voltage is applied to it. Fig. 3c is a copy oi' an oscillogram lized to neutralize a saturable inductance I5 in showing the current wave of a simple self-satseries relation therewit and Fig. 7 shows the urating reactor. Fig. 3d is a copy of an oscillonetwork of Fig. 2 utilized to neutralize the saturgram showing the current wave of a reactor o1' the able inductance I5 connected in parallel relation four-legged type with D. C. bias raised to 80% of therewith. 5 the A. C. excitation. It will be noted that the Fig. 8 diagrammatically illustrates an applicadepends upon the ratio of the D. C. excitation to the current ratio and phase displacement may be the A. C. excitation. Whether a. wave shape is to maintained sensibly constant with a variable bur- 10 be considered good or bad depends on the basis of den connected to the secondary winding of the comparison. In'the present invention the basis transformer. An alternating-current circuit is of comparison is between ythe biased reactor and represented by the conductors I6. A current 'the self-saturating reactor. transformer II has a primary winding I8 con- In Fig. 4, I have diagrammatically illustrated nected 'in series relation with the circuit I6 and 15 the combined v0 -ampere characteristics of the a secondary winding I3 connected to energize the series connected inductance I2'with a ilxed bias useful burden 20 which is very diagrammatically and the capacitory II with the volt-ampere charillustrated by a square outline. In parallel relain accordance with my invention, with applied capacitance comprising a capacitor 2| and a 20 voltage Eac as ordinates and current Iac as abbiased saturable reactor having alternating curscissae. For relatively small values oi series carent windings 22 and a saturating winding 23 pacitive reactance, the characteristic clu've is of connected to be energized from a source of direct the shape Ti. With increasing values 0f Capaci- -current 24. The capacitor 2I may be made adtive reactance the characteristic curves assume justable in order to adjust the desired degree of 25 the forms T2, T3 and T4. Curve T2 is of particusaturation of reactor 22 to be consistent with that lar interest in its horizontal zone a-b, in that of the magnetizing current oi the transformer Il. an inappreciable change in voltage produces a Fig. 9 diagrammatically illustrates a modicalarge Change in current. Curve T3 is of interest tion of the arrangement illustrated in Fig. 6, in with 8.10118 Zero ZOIle O-a, and a dropping Zone which the current transformer I1 is provided 30 b'-C. It 1S t0 be noted that there S a plurality with a primary Winding connected'jrl Series re.. of current values for the Voltage E0- The drOD- lation with the circuit I6 and two secondary ping zone leads to instability and t0 the S0- windings ls and is' connected respectiveiy to called jumping phenomenon in Circuits 0f this the burden zo and the ssturating capacitance type. Curve T4, in addition to showing a plunem/oil.;- rality of current values for a given voltage over a In the simple current transformer, as illuswide range, crosses the current axis at the point trated in Flg 3 Without the compensating means, d, yielding a leading power factor for currents the ratio of transfor leSS than d and a lagging power factor for cur" that of the turn ratio due to the magnetizlng rents greater than flcurrent of the transformer. The magnetizing 40 In Fig. 5, I have dagr-ammatleally illustrated current also causes a departure from the 180 the combined volt-ampere characteristics of the phase relation between the primary and seo- Parallel Cermeeted lnduetence l2 with e fixed ondary currents. These deviations increase with bles and the Capaeller l l correlated ln accordincreasing saturation ofthe transformer core, ance my invention, the applied Voltage and as adequate means have not been known in Ede aS ordinates. lagging Current es Positive the past to compensate for saturating magnetizabSCiSSee, and leading Current ICC es negative ing currents it has become customary to design abscissae. If One takes, fOr exemple, a biased current transformers for very low densities. reactor having a volt-ampere characteristic rep- However, foi` those applications in which the hairesented by curve R of Fig. 3 and connects it in monies and power components of exciting our- 50 parallel with a capacitor having the volt-ampere reni, are not objeotionable, as in Certain relay characteristic represented by curve C1 of Fig. 3 applications, it now beoomes feasible to design there is obtained a volt-ampere characteristic for Current transformers for reasonably high densithe circuit as illustrated by curve T5 of Fig. 5. Jcies with gres larly like a saturating capacitance. In the rent' is substantially eliminated zone e-f the network -still behaves like a capacitance for the total actual current but as an intaneously by lea ductance for increments in the current. At the with increasing point f the phase 0f the Cllrrent reVerSeS from tail in the consideratiOn of curve T5 in Fig. 5.

leading to I agglng I? one Substitutes a capaci" In Fig. 10, I have illustrated an embodiment of tor in the circuit of Fig. 2 having a volt-ampere my invention in a voltage regulating System By characteristic .represented by curve C2 of Fig. `3 Way' of example, I have Shown a Circuit 25 which there is obtlmed a Volt'ampere charactenmc is to be controlled by regulating means shown as for the clrcult as Illustrated b5.' curve T6 Whlch an induction regulator 26 which is provided with a reversible motor 21 for operating the rotor of the regulator in a manner to introduce a voltage 70 t l n at the rvteopignegggam o agg] g component to increase or decrease the supply Figs. 6 and '7 diagrammatically illustrate one v oltaee for regulatmg the load Voltage 0n the general use of my saturating capacitance having circuit 25. The motor 2l -1s illustrated as a twothe characteristic as illustrated by curve T5 of Phase mOtOr llavlllg a Squlrrel eagerOtel 28 C0nr Fig. 5. Fig. 6 shows the network of Fig. 2 utinected through a shaft 29 and suitable gearing 70 30 to the rotor of the regulator. The stator winding of the motor comprises one phase winding 3i connected directly to the circuit 25 and another phase winding 32 connected through a phase sluiting network arranged in the form of a Wheatstone bridge which is connected to be energized from the circuit 25. The phase shiiting network includes a reactor or auto transformer 33 provided with a mid-tap 3l. A resistor 35 is arranged in series relation with a non-linear parallel circuit, similar to the arrangement illustrated in lig. 2. comprising a capacitor 35 and a biased saturable reactor 31, connected in series relation with resistor 35 across the outer terminals of the reactor 33. The reactor 31 is provided with a saturating winding 38 which is connected to be energized through a suitable rectifier 39 from the circuit 25, or any other circuit which is normally designated asa constant potential supply. The motor phase winding 32 is connected to the mid-tap 3l oi! the reactor 33 and to the junction point 40 between the resistor 35 and capacitor 36.

The sensitivity of the arrangement may be greatly increased by adding a parallel connected capacitor 4l and saturable reactor 42 in series relation with the alternating current circuit of the rectier 39.

The operation of the arrangement illustrated in Fig. 10 is substantially as follows: It will be assumed that the capacitor 36 is selected ior parallel resonance with the reactor 31 at approximately the desired voltage on the circuit 25. When the line voltagel is such as to give exact resonance between capacitor 36 and reactor 31, the voltage between the points 3l and lli is in phase with that of the voltage of circuit 25, say vector a, Fig. l1. At increasing voltages this voltage vector will assume progressively changing phase positions like b, c, d and e. At voltages below resonance, it will assume progressively changing phase positions like f, g and h, Vectors c" and g are in quadrature with the line voltage and furnish the necessary quadrature phase voltage to the motor winding 32 to cause the motor to run in one direction or the other depending upon the energlzation of winding 32. This causes the voltage regulator 26 to boost or buck the line voltage in a manner well understood by those skilled in the art.

In the foregoing description oi various embodiments of my invention it will be observed that the bias of the saturable inductance has been held constant or substantially constant. In the following description other embodiments o! my invention are described in which the bias cf the saturable inductance is varied in a manner tcmaintain a constant ratio between the direct current and the alternating current of the induct-ance.

Fig. 12 illustrates diagrammatically an elementary circuit arrangement for explaining the embodiments of my invention shown in Figs. 15 and 17 and comprises the alternating current source ill connected to energize the biased saturable inductance i2 comprising the alternating current windings I2' and the saturating winding i3 connected to be energized from a rectiiler I3 in accordance with the current traversing the alternating current windings of the inductance. As illustrated, the rectifier may be of the dry contact type connected for full wave rectiiicacation with the input terminals connected in series relation with the windings I2 across the source I l and the output terminals connected w the winding I3.

Fig. 13 illustrates diagrammatically the voltamperc characteristics or the arrangement shown in Fig. l2 with di'erent ratios between the direct and alternating current excitation o! the inductance. The curves are plotted between the voltage Eac applied to the inductance as ordinates and the current Iac through the inductance as abscissae. The curve T1 is the characteristic curve when the direct current excitation is zero or negligible compared with the alternating current excitation. The curve Tn is obtained when the direct current excitation is increased over that used in obtaining curve T1. It will be observed that Ts shows flatter alternating current saturation than T1. Curve To is intended to show the case when the direct current excitation is increased sufficiently to obtain a perfectly fiat saturation zone. The ratio o! the direct current excitation to alternating current excitation which gives this characteristic, dii'lers with different magnetic materials; but, for the more important ferro-magnetic materials, this ratio is of the order of one-half to one and onehalf. Curve T10 is obtained with a still further increase in direct current excitation and is oi interest by the drooping zone of its characteristic curve and susceptibilty to instability or the jumping" phenomenon oi non-linear circuits under suitable conditions.

Starting with a saturable inductance of which the alternating current characteristic is oi the general shape of curve Tf1 with zero direct current excitation, characteristic curves Ta, To and Tia can be obtained by connecting suitable capacitors in series with the inductance, without the aid of any direct current bias, but with much greater wave distortion. In accordance with my invention I employ a direct current bias partially to replace the necessary series capacitance andthereby obtain better wave shape. greater stability and in addition convenience and economy in those cases in which the circuit voltage may be too high or too low for the available capacitors.

It will be observed that in a circuit with a nonsaturating inductive reactance in series relation with a biased saturable inductive reactance, ilatness oi saturation of the resultant characteristic curve can be accomplished by making the saturable inductive reactance suiilciently drooping, as shown by curve T10 of Fig. 13, to compensate for the rising characteristic of the non-saturating inductive reactance, and thereby obtain a resultant characteristic curve like curve To of Fig. 13. In this respect, then, means are disclosed whereby an inductive means may neutralize an inductive reactance.

The high degree of the fiatness of saturation of curve To lends itself admirably well to circuit voltage control. In accordance with my invention the arrangement of Fig. l2 is combined with a shunt capacitance, to make its power factor leading or lagging with small changes in circuit voltage, and with a series capacitance to adjust the slope of the characteristic curve. Applications of this embodiment of my invention to circuit control are shown in Figs. l5 and 17.

Referring again to Fig. l2, a load device Il is connected across the biased saturable inductance l2, and the supply circuit impedance is represented by the inductances 45. Let Eo be the desired voltage to be held across the load This voltage regulating characteristic of this type of saturable inductance. functions just as Well whether the tendency to variations in the circuit voltage is brought about by variations in the load ment the source biased saturable inductance I2 design as illustrated in Fig. 12. A capacitor 46 is connected in series with the inductance winding l2' to adjust curve.

A tendency of the load voltage to rise above Eo will cause the combination to draw a relatively large lagging current, thereby tending to lower the voltage across the load. On the other hand, a tendency drop below Eo will cause the combination to draw a relatively large leading current from the circuit, thereby tending to raise the voltage through the induit-tive impedance of the circuit. Fig. 17 shows the circuit arrangement illustrated in Fig. 15 slightly modied to obtain a constant reference voltage Eo over a wide range of supplyl voltage across a feeder. This modiiication consists of the introduction of the inductance 48 in series with the feeder lines to be regulated by the saturable inductance I2. 'Ihe range of supply voltage over which the arrangement can the special charoperated over the critical region specified produces greater sensitivthe magnetic density of said core,

5 embodiments of my invention it will be obvious to those skilled in the art that various changes and modications may be made without departing from my invention in its broader aspects, and I therefore aim in the appended claims to cover changes and modications asfall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an alternating current circuit including a. reactive current device comprisampere characteristic, and means for controlling the magnetic density of said core being of a value substantially to reduce wave distortion in said alternating current circuit.

2. In combination, an alternating current ciruit including a capacitance and a saturable inductance comprising a magnetic core and an alternating current winding connected in circuit with said capacitance, and a circuit for estabunidirectional flux in said core, the unidirectional ilux of said core being of a value magnetically to bias said inductance to minimize wave distortion in said alternating current circuit.

3; In combination, an alternating current circuit,

ampere characteristics of said elements as to provide a total volt-ampere characteristic for said the respective volt-ampere characteristics of said elements as to provide a total volt-ampere characteristic having the properties oi a capacitance for a predetermined range of voltages and an inductance for a diierent predetermined range of voltages.

volt-ampere characteristic simultaneously for varying applied voltage between predetermined limits.

7. In an electric circuit, a reactive current device comprising a biased saturable reactor and a capacitor connected in parallel relation in said circuit, each of said elements having a voltampere characteristic such that the current to said device leads the voltage across said device and varies non-linearly to exhibit a steady state saturating capacitance volt-ampere characteristic for increasing applied voltage.

8. In combination, an inductive device having a non-linear volt-ampere characteristic and a reactive current device comprising a capacitive element and a biased inductive element arranged for neutralizing the inductive reactance of said inductive device for the non-linear portion of its volt-ampere characteristic.

9. In combination, a saturating reactor, and a saturating capacitance in series relation therewith comprising a capacitor and a biased saturable reactor connected in parallel relation.

10. In combination, a saturating reactor, and a saturating capacitance in parallel relation therewith comprising a capacitor and a biased saturable reactor connected in parallel relation.

11. In combination, a current transformer, an electric burden connected to said transformer, and a reactive current device connected to said transformer and comprising capacitive and inductive elements in combination, each of said elements having a volt-ampere characteristic such that power factor of said device is leading and exhibits saturation simultaneously for variation in applied voltage.

12. In combination, a current transformer, a power consuming device connected to said transformer, and a saturating capacitance in parallel relation to said power consuming device and comprising a capacitor and a biased saturable reactor connected in parallel relation.

13. In combination, an alternating current circuit, a reactive current device comprising a capacitive element and a biased inductive reactive current element in combination in said circuit, each of said elements having a volt-ampere characteristic such that the power factor of said circuit is leading for total current and lagging for increments of current.

114. In an electric circuit, a reactive current device comprising a capacitor and a biased saturable reactor connected in parallel relation, each of said elements having a volt-ampere characterlstic such that the power factor of said circuit is leading for total current and lagging for increments of current.

15. In an electric circuit, a reactive current device comprising capacitive and biased inductive reactive current elements in combination, each o! said elements having a volt-ampere characteristic such that a plurality of different voltage values of said circuit correspond to a single current value during a continuous change in applied voltage in the same direction.

16. In an electric circuit, a reactive current device comprising a capacitor and a biased saturable reactor connected in parallel relation, said capacitor and said reactor each having a volt-ampere characteristic such that a plurality of different voltage values of said circuit correspond to a single current value during a continuous change in applied voltage in the same direction.

17. In an electric circuit, a reactive current device comprising a capacitive element and a biased inductive reactive current element in combination, each of said elements having a volt-ampere characteristic such that a plurality of di!- !erent current values of said circuit correspond to a single voltage value during a continuous change in applied voltage in the same direction.

18. In an electric circuit, a reactive current device comprising a capacitor and a biased saturable reactor connected in series relation, said capacitor and said reactor each having a voltampere characteristic such that a plurality oi different current values o! said circuit correspond to a single voltage value during a continuous change in applied voltage in the same direction.

19. In combination, a phase shifting network comprising a mid-tap reactor, a resistor and a parallel connected capacitor and saturable reactor, connected in the form ci a bridge circuit, and a source of voltage'connected to energize said bridge at alternate junction points therein, said capacitor and saturable reactor each having a volt-ampere characteristic such that a voltage component across the remaining junction points o! said bridge circuit varies oppositely in phase with said applied voltage depending upon whether said applied voltage is above or below a predetermined value.

20. In an alternating current circuit, a saturable reactor having a magnetic core, direct current means for independently controlling the ilux density of said core, a capacitance in series circuit with said reactor for determining the slope oi' its volt-ampere characteristic, and a second capacitance connected in parallel relation with a circuit including said reactor for selectively determining the power factor of the combined circuit in accordance with the voltage applied thereto.

21. In an valternating current circuit, a saturable reactor having a magnetic core, direct current means for independently controlling the iiux density of said core to maintain a constant ratio between the alternating current excitation and the direct current excitation, a capacitance in series relation with said reactor, a second capacitance connected in parallel relation with a circuit including said reactor, and an impedance element connected in circuit with said reactor to be traversed by the combined current of said reactor and capacitance elements.

22. In combination, a source of variable alter nating voltage, a saturable reactor having an alternating current winding and a magnetic core, a second winding on said core ior independently controlling the ilux density of said core, a rectiiler having its input terminals connected in series relation with said reactor and its output terminals connected to energize said second winding, a capacitance connected in series relation with said reactor, a second capacitance connected in parallel relation with said reactor and said capacitance, and a reactor connected in series relation with said saturable reactor and capacitance elements and arranged to provide a steeply rising volt-ampere characteristic for its normal range of operation whereby a substantially constant branch voltage exists across said saturable reactor and series connected capacitance irrespective o! variations in the voltage oi' said source of alternating voltage.

ARAM BOYAJIAN. 

